This invention relates to clips for mounting heat sinks to circuit boards.
Many circuit devices, including integrated chips, generate heat during operation which must be dissipated to avoid damage to the circuit device. In many cases, heat generated by the circuit devices is adequately dissipated through a ground plane of the circuit board to which the circuit device is connected, or into the environment surrounding the circuit board. Where the density of the operating circuit devices is so high that heat cannot be adequately dissipated through circuit connections or into the atmosphere, it is common to employ heat sinks to aid in dissipation of heat to the environment. Moreover, it is common to mount circuit devices directly to heat sinks which themselves are mounted to the circuit board.
Heat sinks are constructed of thermally conductive material such as copper or aluminum, and include fins to increase the surface area of the heat sink to increase heat transfer from the heat sink to the air surrounding it. Heat sinks are commonly mounted to circuit boards by surface mount techniques. Pads on the circuit board provide a solder mount for the heat sink or a clip holding the heat sink. A circuit component is mounted to the heat sink and the component and heat sink are mounted to the board, the heat sink being mounted to the pads to dissipate heat from the circuit component attached thereto. In some cases, the heat sink or pads are connected to a ground plane in the circuit board to additionally dissipate heat from the circuit board.
One example of surface-mounted heat sinks may be found in the Jordan et al. U.S. Pat. No. 4,625,260. In Jordan et al., a surface mount clip fastener is soldered to pads on the circuit board, and a heat sink is mounted to the clip. One of the problems with the Jordan et al. approach is that mounting the clip fastener requires an additional solder step of the surface mount. A jig or other holding mechanism is required to hold the clip in place while soldering the clip fastener to the pads, thereby adding to the fabrication costs. Moreover, permanently mounting the clip fastener to the circuit board, such as by surface mount solder connection as in Jordan et al., obscures portions of the circuit board and pad from inspection, thereby rendering final inspection and test of the circuit board more difficult. Consequently, there is a need for a clip fastener for mounting a heat sink to a circuit board that permits temporary mounting of the clip fastener to the board to permit inspection and testing, and that permits subsequent permanent attachment without use of a jig or other holding mechanism.